1. Field of the Invention
This invention relates to the field of overhead electrical distribution systems and, more particularly, to such a system provided with a six conductor pre-wired overhead raceway to which pre-wired cables may be selectively connected to provide either switched power or continuous, unswitched power to dual-ballasted fluorescent lamp fixtures.
2. Description of the Prior Art
It is broadly known to provide an overhead electrical distribution system for selectively supplying power to a plurality of ceiling-mounted fluorescent lamp fixtures coupled to a plurality of branch circuits which are connected to a common power bus. One such prior art system is shown in U.S. Pat. No. 4,001,571. However, in this prior art system, each branch circuit consists of the conventional four conductors: two hot conductors, a neutral conductor and a ground conductor. The lamp fixtures contain four-socket receptacles, and fixtures are connected to the power bus by means of a cable having a matching four-prong plug on one end thereof, the other end thereof being wired to a junction box on the power bus. Adjacent lamp fixtures may be interconnected by cables having four-pronged plugs on opposite ends thereof, one of the plugs also having a four-socket receptacle for receiving another plug. In order to provide switched power to a single lamp fixture or to a group of lamp fixtures, a switch adaptor must be inserted into a branch circuit or between a branch circuit and the fixture or group of fixtures. The switch adaptor must be wired to a wall switch. Furthermore, all of the plugs are not identical, and all of the receptacles are not identical.